Laser Raman spectroscopy detects gases by analyzing the scattered light from a laser beam interacting with gas molecules. A laser is directed at the gas sample, and most light scatters elastically, but some scatters inelastically, shifting in wavelength due to molecular vibrations. This shifted light, known as Raman scattered light, is collected and analyzed to identify the gas and determine its concentration based on its unique vibrational fingerprints. This method offers high sensitivity and specificity.